A protein that breaks, swivels, and rejoins DNA strands.Group of answer choicesprimasesingle-strand binding proteinOkazaki fragmenthelicasetopoisomerase

To determine which protein is responsible for breaking, swiveling, and rejoining DNA strands, let’s analyze the available choices:

1. Primase: This enzyme synthesizes RNA primers needed for DNA replication but does not break or rejoin DNA strands.

2. Single-strand binding protein: This protein binds to single-stranded DNA during replication to prevent strands from re-annealing or forming secondary structures but does not modify the DNA itself.

3. Okazaki fragment: This is not a protein but rather a short segment of DNA synthesized on the lagging strand during DNA replication.

4. Helicase: This enzyme unwinds the DNA helix by breaking hydrogen bonds between base pairs but does not perform the action of rejoining DNA strands.

5. Topoisomerase: This enzyme relieves the strain of twisting and supercoiling during DNA replication by cutting the DNA, swiveling to relieve tension, and then rejoining the DNA strands.

Final Answer

Topoisomerase is the protein that breaks, swivels, and rejoins DNA strands.